Catalytic cracking with silver-rare earth or copper-rare earth exchanged y-type zeolite

ABSTRACT

A SILVER-RARE EARTH OR COPPER-RATE EARTH EXCHANGE ZEOLITE CRACKING CATLYST CAPABLE OF PRODUCING HIGH OCTANE GASOLINE OF INCREASED AROMATIC CONTENT. SILVER OR COPPER IONS IN COMBINATION WITH RARE EARTH IONS ARE EXCHANGED INTO A SYNTHETIC Y-TYPE ZEOLITE USING A COMBINATION OF EXCHANGE AND CALCINATION STEPS. THE EXCHANGED ZEOLITE IS ADVANTAGEOUSLY COMBINED WITH A MAJOR PORTION OF INORGANIC OXIDE MATRIX TO PRODUCE A CATALYST SUITABLE FOR USE IN STANDARD COMMERICAL FLUID AND MOVING BED CAT-CRACKING UNITS.

3,835,032 CATALYTIC CRACKHNG WITH SILVER-RARE EARTH R COPPER-RARE EARTHEX- CHANGED Y-TYPE ZEOLITE Geoifrey E. Dolbear, Columbia, and John S.Magee, Cooksville, Md., assignors to W. R. Grace & C0,, New York, N.Y.

N0 Drawing. Continuation-impart of abandoned application Ser. No.166,243, July 26, 1971. This application Mar. 26, 1973, Ser. No. 344,963

Int. Cl. Clog 11/02 US. Cl. 208-120 6 Claims ABSTRACT OF THE DISCLOSUREA silver-rare earth or copper-rare earth exchanged zeolite crackingcatalyst capable of producing high octane gasoline of increased aromaticcontent. Silver or copper ions in combination with rare earth ions areexchanged into a synthetic Y-type zeolite using a combination ofexchange and calcination steps. The exchanged zeolite is advantageouslycombined with a major portion of inorganic oxide matrix to produce acatalyst suitable for use in standard commercial fluid and moving bedcat-cracking units.

This application is a continuation-inpart of application Ser. No.166,243 filed July 26, 1971, and now abandoned.

The present invention relates to hydrocarbon cracking catalysts, andmore specifically to improved zeolite cracking catalyst compositionswhich are capable of producing a high yield of aromatic gasolinefractions of enhanced octane rating.

It is generally known that hydrocarbon cracking catalysts which arepromoted with stabilized zeolites, particularly ion exchanged syntheticfaujasite, i.e., Y-type zeolite, are capable of producing high yields ofgasoline fractions from petroleum feedstocks such as gas oil. Thesecracked gasoline fractions are subsequently combined with octaneenhancing additives such as tetraethyl lead to produce high octane motorfuel.

Recent emphasis on air pollution control has dictated a need forremoving metal type octane enhancing additives from commercialgasolines. To produce non-leaded gasoline of sufficient octane ratingfor use in modern automobile engines it is generally necesseary for therefiner to use a blend of petroleum gasoline fractions which are ofinherently high octane rating. Highly aromatic gasoline fractions are ofparticular use to the refiner. Unfortunately, however, gasolinefractions produced by the cat-cracking of gas oil using normal amorphousand crystalline zeolite type cracking catalysts are of relatively lowaromatic content. Accordingly, relatively expensive subsequent catalytictreatment is generally required to increase the aromatic content, andhence the octane rating of cat-crack gasolines, and thereby avoid theaddition of lead type octane enhancing additives.

It is therefore an object of the present invention to providecat-cracked gasoline fractions which possess an increased aromaticcontent.

It; is another object to provide an improved catalytic cracking catalystcomposition which is capable of producing a high yield of gasolinefractions which exhibit increased octane rating without the addition ofoctane enhancing additives.

United States Patent 0 3,835,032 Patented Sept. 10, 1974 It is stillanother object to provide a highly active metal exchanged zeolitecatalyst which is capable of cracking petroleum hydrocarbon feedstocksto produce highly aromatic type gasoline fractions.

It is yet another object to provide a metal exchanged syntheticfaujasite containing fluid cat-cracking catalyst which is suitable foruse in commercial cracking units and which is capable of producinggasoline of inherently h1gher octane rating than normally obtained usingzeolite promoted cat-cracking catalysts.

It is yet a further object to provide a metal exchanged type zeolitecat-cracking catalyst which will produce high yields of aromaticgasoline without producing attendant excessive quantities of undesirablecoke and dry gas fractions.

These and still further objects of the present invention will becomereadily apparent to one skilled in the art from the following detaileddescription and specific examples.

Broadly, our invention contemplates a zeolite cracking catalyst whichcomprises synthetic Y-type zeolite exchanged with silver or copper ionsin combination with rare earth ions.

More specifically, we have made the surprising finding that a Y-typezeolite having a silica to alumina ratio in excess of about 3.0 whichhas been ion exchanged from about 1 to 10% by weight silver ionsexpressed as Ag O or copper ions expressed as CuO, and from about 3 to15% by weight rare earth ions expressed as REZOQ will catalyze thecracking of petroleum to produce gasoline fractions of unusually higharomatic content. Even more surpunsmg, is our finding that the presentsilver or copper rare earth exchanged Y-type zeolite, i.e., Ag-RE-Y orCu-RE-Y contemplated herein, when used as a hydrocarbon crackingcatalyst or catalyst additive, will produce only minor amounts ofundesirable coke and/or dry gas fractions.

The presently contemplated Ag-RE-Y and Cu-RE-Y catalyst may be producedby one of two techniques. In general, the first technique involves thefollowing steps:

1) A sodium Y-type zeolite possessing a silica to alunnna ratio inexcess of about 3 is exchanged with ammomum salt solution, such asammonium sulfate or ammon1um chloride, to reduce the sodium oxide (Na O)level of said sodium Y-type zeolite to about 1.5 to 4% by weight.

(2) The ammonium salt exchanged zeolite is then exchanged with a rareearth salt solution, either rare earth chloride or rare earth sulfate,to impart a RE O content of from about 0.3 to 15 by weight.

(3) The rare earth exchanged zeolite is then calcined at a temperatureof about 7001600 F. for a period of 0.1 to 3 hours.

(4) Subsequently, the calcined exchanged zeolite is exchanged again withammonium salt solution to lower the soda content to less than about 1%by weight.

(5) The above reexchanged zeolite is then contracted with a solution ofsilver or copper ions, preferably silver nitrate or copper chloride toimpart a silver or copper content measured as Ag O or CuO of from about1 to 10% by weight.

(6) The Ag-RE-Y or Cu-RE-Y exchanged zeolite is then calcined at atemperature of from about 500 to 1400 F. for a period of 1 to 10 hours.

A second procedure which may be used to prepare the presentlycontemplated Ag-RE-Y or Cu-RE-Y cataylst involves the following generalprocedure:

(1) A synthetic sodium Y-type zeolite having a silica to alumina ratiogreater than about 3 is exchanged with a solution which contains amixture of silver or copper and rare earth ions, preferably rare earthnitrate, at a pH of from about 3.0 to 3.5. This procedure imparts asilver-rare earth or copper-rare earth content of from about 1 to 12% byweight measured as RE O and 1 to by weight silver or copper measured asAg O or CuO.

(2) The exchanged zeolite is then calcined at a temperature of fromabout 800 to 1400 F. for a period of about 1 to 3 hours.

(3) The calcined silver or copper-rare earth exchanged zeolite is thenexchanged with an ammonium salt solution, such as ammonium sulfate, tolower the soda content to below about 0.5% by weight.

(4) The exchanged zeolite is then calcined at a temperature of fromabout 500 to 1400 F. for a period of 1 to 10 hours.

Optionally, the catalysts prepared above may be reduced in hydrogenatmosphere at a temperature of about 400 to 1200 F. for /2 to 10 hoursprior to use.

The catalysts contemplated in the present invention may comprise eitheressentially 100% Ag-RE-Y or Cu-RE-Y or the catalyst may comprise Ag-RE-Yor Cu-RE-Y admixed with an inorganic oxide component. Where it isdesired to obtain a catalyst in fluidized or pelleted form, theprecursor synthetic sodium- Y-type zeolite ingredient may be in the formof a formed fiuidizable or pelleted particle. This fluidized or pelletedparticle is subjected to the above exchange and calcination proceduresto obtain a catalyst product which is essentially all Ag-RE-Y orCu-RE-Y.

When it is desired to obtain a catalyst which contains Ag-RE-Y orCu-RE-Y admixed with an inorganic oxide matrix, the Ag-RE-Y or Cu-Re- Yin finely divided form is blended with a suitable inorganic oxide matrixcomponent. Suitable matrix components are generally described in theprior art, and may be selected from inorganic hydrogels such as silica,alumina and silica alumina hydrogel. In general, these hydrogelcomponents are essentially amorphous and are readily blended with thehighly crystalline Ag-RE-Y or Cu-RE-Y component. It is also contemplatedthat matrix components such as clay and combinations of clay withamorphous inorganic hydrogels may be combined with the presentlycontemplated Ag-RE-Y or CuRE-Y catalyst component.

As indicated above, the catalysts contemplated herein may be obtained influid form wherein finely divided spray dried microspheres having aparticular size range of from about 10 to 150p. are obtained usingconventional catalyst preparation techniques. It is also contemplatedthat catalysts suitable for moving or fix bed operation wherein thecatalyst particle size ranging from about 5 to 40 mesh may also beobtained using standard catalyst preparation procedures.

The present catalysts are used in the cat-cracking of heavy petroleumfeedstocks. Preferably the catalysts are utilized in a conventionalmanner where the petroleum feedstock such as gas oil is contacted with abed of the catalyst at a temperature of from about 800 to 1000 F. Thecontact time of the petroleum feedstock with the catalyst will dependupon the specific catalytic process employer; however, it is found thatcontact times as low as 5 seconds up to 300 seconds may beadvantageously employed using the highly active catalyst of the presentinvention.

When the present catalyst is used in combination with a typicalsemi-synthetic matrix, i.e., a matrix comprising silica alumina hydrogeland clay, wherein the Ag-RE-Y or Cu-RE-Y component is present in amountsranging from about 5 to by weight, the catalyst will exhibit amicroactivity on the order of from about 60 to 85 when tested understandard conditions. The product distribution obtained using the presentcatalyst revealsthat high yields of gasoline fractions (C through C areobtained. These gasoline fractions posses an extraordinarily higharomatic content which is readily measured using standard NMRtechniques. It is also found that the present catalysts produce acracked product which contains only small quantities of undesirable drygas (hydrogen, C and C products and only small amounts of coke. Thisresult is entirely unexpected in that it is generally found that theaddition of metals such as silver to ordinary catalyst generallyincrease the dry gas and coke production levels to levels which are notacceptable in commercial cracking processes.

Having set forth the basic aspects of the present invention, thefollowing examples are given to illustrate specific embodiments thereof.

EXAMPLE I A 200 g. sample of commercial sodium Y-type zeolite containing13% Na O and having a silica to alumina ratio of 5.1 was dispersed in 2liters of deionized water which contained 200 g. of ammonium sulfate.The mixture was heated to boiling and maintained at that temperature forone hour. The subsequent exchanged solid product was collected on afilter, rinsed with deionized water and then reexchanged with 2 litersof ammonium sulfate solution which contained 200 g. of ammonium sulfate.The solid product was collected and then admixed with 1 liter of rareearth chloride solution which contained the equivalent of 12 g. rareearth oxides. The rare earth solution was heated to boiling for 30minutes and the solids subsequently collected. The solids were rinsedfree of sulfate and chloride and then calcined at 3 hours at 1400 F. Thecalcined product was then exchanged twice with ammonium sulfate asdescribed previously and rinsed sulfate free. One-half of the resultantproduct was exchanged with 25 g. of silver nitrate dissolved in 250 ml.of water at 60 C. The other half of the calcined product was similarlyexchanged with 50 g. of silver nitrate solution. The resultantsilver-rare earth exchanged zeolite was then calcined for 3 hours at1400 F. The resultant Ag-RE-Y possessed a surface area of 551 and 554 m.g. respectively.

Example H The Ag-RE-Y products obtained above were analyzed for silverand rare earth content. These analyses are set forth in Table I below.These samples of Ag-RE-Y were combined in a semi-synthetic crackingcatalyst matrix which comprised 30 parts by weight kaolin clay and 60parts by weight silica-alumina hydrogel. The hydrogel contained 25% byweight alumina. The Ag-RE- Y was combined in amounts of 10% by weightwith the synthetic matrix and subsequently formed into inch pills. Thesepills were heat treated at 1350" F. for 16 hours at steam at 15 p.s.i.g.to stimulate commercial deactivation. The steamed pills were then usedto crack gas oil at a temperature of 920 F. and a weight hourly spacevelocity of 4.3 in a standard microactivity unit. The cracked gas oilwas examined for aromatic content using the nuclear magnetic resonancetechnique fully described in US. Pat. 3,693,071. (Application 80,830,filed Oct. 15, 1970 by G. E. Dolbear.)

The catalyst analysis and cracked product distributions are set forth inTable I below. Included in Table I are the product distributions for astandard calcined rare earth type Y (CREY) which was prepared by way ofa similar technique which does not contain silver. The results belowclearly indicate that the Ag-RE-Y catalyst produced gasoline having asubstantially higher aromatic content. This aromatic content is clearlyrelated to a higher octane characteristic.

TABLE I Microactivity results To determine the effect of reducing theabove catalysts with hydrogen prior to use, samples of the catalysts setforth in Table I were reduced in flowing hydrogen for 2 hours at 900 F.prior to steaming. Microactivity reparts by weight 25%alumina-silica-alumina used in Example III. The Ag-RE-Y was combinedwith the matrix at a level of by weight. This product was pilled,steamed and subjected to the micro-activity test sults are set forth inTable II below. previously set forth in Example II. The results are setforth below in Table III. TABLE II TABLE 111 Molecular sievecomposition, Microactivity Molecular sieve percent of resultscomposition Microactivity percent of results Volume Percent percentPercent aromatic Volume Percent Sample No. Ag B11 03 conversion cokeprotons percent Percent aromatic Sample No. Ag O RE2O3 conversion cokeprotons 4 9.5 4.1 73.7 4.1 17.4

From the above, it is concluded that hydrogen reduction of the catalystfurther increases its aromatic enhancement properties.

Example III A 100 g. sample of commercial sodium Y-type zeolite having asoda content of 13% and a silica to alumina ratio of about 5.1 wasdispersed in a solution which contained 39.9 g. of lanthanum nitrate(LaNO -6H O), which is equivalent to 15.0 g. La O and 2.94 g. of silvernitrate, which is equivalent to 2.0 g. Ag O, in 250 g. water. The pH ofthe lanthanum nitrate-silver nitrate solution was adjusted to 3.1 by theaddition of nitric acid. The dispersion of sodium Y zeolite in thesilver lanthanum nitrate solution was heated to boiling for 1 hour, andthe solids were recovered by filtration. The solids were washed withdeionized water until no traces of silver were detected. The exchangedproduct was then calcined for 3 hours at 1000 F. and then reexchangedusing two boiling exchanges with a solution which comprised 100 g. ofammonium sulfate dissolved The above data clearly indicates that ascompared to a standard zeolite promoted cataly st which only containsrare earth ions, the silver containing zeolite of the present inventionproduces substantially greater aromatics as indicated by the increasedaromatic proton content.

Example V Samples of Ag-REY catalysts mixed with a matrix containing 30parts clay and parts silica-alumina (25% A1 0 such as set forth inExample II were subjected to pilot plant testing using two differenttypes of gas oil. The West Texas Gas Oil (WTGO) possessed a gravity of27.7 API and a boiling range of 610 to 920 F. The Sun Oil gas oil (Sun)possessed a gravity of 30.7 API and a boiling range of 350 to 980 F. Forpurposes of comparison, samples of catalysts having similar activitywhich contained various amounts of rare earthhydrogen type Y zeolitemixed with a synthetic silicaalumina (26% Al O matrix were also rununder similar conditions. The results of the pilot plant testing are setforth in Table IV below.

Conversion, volume percent. 66

C1+Cz, weight percent FEE... 1.65 1.12 Total Cg's, volume percent FF 0.7Total 04's, volume percent FF (ll-volume percent FF.. 0.4-

(.Hgasoline, volume per- 49.0 5

cent FF. Octane No.:

Research (AS'IM) 92.8 88.8 00.4 80.7.

Motor (ASTM) 78.2 77.1 77.0 76.1. Aniline point F.. 72.. 80.. "0. 82.Bromine No 82.. 51 47...

Coke, weight percent FF 5.7 4.5 5.6 3.0.

1 1,350% K; 160% steam; 12 hours. 2 1.520% F.; 20% steam; 12 hours.

in 1 liter of water. The exchanged product was then It is seen from theabove data that catalysts A and C washed to remove sulfate and driedovernight at 250 F. of the present invention produce gasolines having asig- Example IV The silver-rare earth Y zeolite prepared by way ofExample III was combined in a semi-synthetic matrix nifican-tly greateroctane than rare earth exchanged type Y catalyst samples B and D. It isalso noted that sample A and C produced greater quantities ofunsaturated C fraction (Cf) than the comparison sample B and D. The

which comprised 30 parts by weight kaolin clay, 60 7 increase in Cproduction is totally unexpected. The C fraction is considerablyvaluable to refiners for use in a'lkylation processes used to obtainhigh octane gasoline.

:Example VI Preparation of Cu-RE-Y A 300 g. sample of sodium type Yzeolite (Na-Y) having a silica to alumina ration of 4.9 was mixed with1.2 l. of Water and 150 g. of ammonium sulfate (NH 80 and 11 ml. ofconcentrated sulfuric acid (H 50 The mixture was heated at boiling for 1hour, then the zeolite was recovered and washed free of sulfate withWater. The zeolite was then exchanged with rare earth chloride byheating at boiling with a solution of 24 g. of mixed rare earthchlorides dissolved in 1.2 1. water. The zeolite was washed with waterand calcined for 3 hours at 1400 F. The calcined zeolite was exchangedwith a solution which contained 300 g. ammonium sulfate dissolved in 3'l. of water. The zeolite was Washed sulfate free then exchanged with asolution which contained 16.2 g. CuCl '2H O dissolved in 750 ml. H O.The resulting Cu-RE-Y zeolite was then calcined for 3 hours at 1000 F.This 'Cu-RE-Y contained 2.3 wt. percent CuO and 5.7 wt. percent RE OExample VII Preparation of Catalysts (A) Various amounts of CuRE-Yprepared by the procedure set forth in Example VI were slurried in 200ml. of H 0. The zeolite slurries were then mixed with various amounts ofa tfinely divided semi-synthetic amorphous cracking catalyst basecomposition which comprised 30% kaolin clay and 70% amorphoussilica-alumina hydrogel mixed in 150 ml. water. The composition wasdried, pilled, and steam deactivated by treatment with 15 p.s.i.g. at1350 F. for 8 hours.

(B) The above procedure was repeated; however, various amounts of RE-Yzeolite were used which was prepared by the procedure set forth inExample I without the copper exchange step. This RE-Y zeolite is used asa blank to compare the selectivity characteristic of the present Cucontaining zeolites with a typical prior art RE exchanged zeolite.

Example VIII Various catalyst samples prepared by the methods set fort-hin Example VII above, which contained Cu-RE-Y having various metal ioncontents, were tested for hydrocarbon cracking activity. The crackedhydrocarbon products resulting from the test (syncrude) were analyzed bygas chromatography for the major olefin fraction of the C product and byNuclear Magnetic Resonance for aromatic protons using the procedure setforth in US. Pat. 3,693,071 to Doibear. The cracking activity test wasconducted at 920 F. using West Texan Gas Oil, a weight hourly spacevelocity (WHSV) of 16 and a catalyst to oil ratio of 5.8. The resultsare set forth in Table V below.

8 the octane member of gasoline is generally proportional to olefins andaromatic content, the presently disclosed cracking catalyst compositionprovides a means by which a petroleum refiner can produce a higheroctane gasoline directly from his catalytic cracking unit.

The above examples clearly indicate that valuable cracking actalystcompositions may be obtained using theteachings of the presentinvention. These compositions are capable of producing commercialquantities of cat-cracked gasoline which possess a higher aromaticcontent than gasolines heretofore obtained using standard zeolitecontaining catalysts.

We claim:

1. A process for increasing the aromatic content of the gasolinefractions recovered from catalytic cracking of hydrocarbons whichcomprises contacting said hydrocarbons under catalytic crackingconditions with a thermally stable zeolite selected from the groupconsisting of silver-rare earth exchanged Y-type zeolite and copper-rareearth exchanged Y-type zeolite, said zeolite having a silica to aluminaratio greater than about 3, a silver or copper content of about 1 to 10%by weight expressed as Ag O or CuO and 1 to 15% by weight rare earthexpressed as RE O admixed with from 50 to 95 weight percent of aninorganic oxide matrix.

2. The process of Claim 1 wherein the matrix is selected from the groupconsisting of silica-alumina and silicaalum'ina hydrogels, clay andmixtures thereof. i

3. The process according to Claim 1 wherein the zeolite is prepared by aprocedure which comprises:

(a) exchanging a sodium Y-type zeolite with a solution of rare earth andsilver ions or a solution of rare earth and copper ions at a pH of fromabout 3.0 to 3.5 to impart the desired silver or copper and rare earthcontent;

'(b) calcining said exchanged zeolite at a temperature of 800 to 1400 F.for about 1 to 3 hours; and

(c) exchanging said calcined zeolite with an ammonium salt solution tolower the Na O content thereof to below about 0.5% by weight.

4. The process according to Claim 1 wherein the zeolite is prepared by aprocedure which comprises:

(a) exchanging .a sodium Y-type zeolite with an ammonium salt to lowerthe Na O content thereof to about 1.5 to 4% by weight;

(b) exchanging said zeolite with rare earth ions to impart the desiredrare earth content;

(c) calcining said rare earth exchanged zeolite at a temperature of 700to 1600 F. for a period of from about 0.1 to 3 hours;

(d) exchanging said calcined zeolite with an ammonium salt solution tolower the soda content to less than about 1% by weight;

(e) exchanging said zeolite with a silver or copper salt solution toimpart the desired silver or copper content; and

(f) calcining said exchanged zeolite at a temperature of from about 500to 1400 F.

The above data in Table V conclusively shows that cracking catalysts ofthe present invention (Samples 1, 2, 3 and 4) which contain copper arehighly active and cap-able of producing consider-ably greater quantitiesof both olefins and aromatics than a typical non-copper containing priorart catalyst (Sample 5). In view of the fact 5. The process according toClaim 1 wherein the zeolite is a silver-rare earth exchanged type Yzeolite.

6. The process according to Claim 1 wherein the zeolite is a copper-rareearth exchanged type Y zeolite.

(References on following page) 9 10 References Cited DEIJB'E'RT 1E.GANTZ, Primary Examiner UNITED STATES PATENTS J. W. HEULWEGE, AssistantExaminer "3,508,867 4/1970 Frilette et a1. 252-455 Z 3,607,043 9/1971McDaniel 208-120 3,591,488 7/1971 1Eber1y et a1. 208-'120 5 2s2 455 23,647,682 3/1972 Rabo et a1 208-420

